[PATCH] ipa: libipa: vector: Add element-wise division operator

[Milan Zamazal]

Hi Laurent,

thank you for the patch.

Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:

> Add an operator to divide a scaler by a vector element-wise. Use it in
> the rkisp1 AWB algorithm to replace manual operation on individual RGB
> components.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/ipa/libipa/vector.cpp         | 10 ++++++++++
>  src/ipa/libipa/vector.h           | 11 +++++++++++
>  src/ipa/rkisp1/algorithms/awb.cpp |  6 +-----
>  3 files changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/src/ipa/libipa/vector.cpp b/src/ipa/libipa/vector.cpp
> index 8019f8cfdc85..f665813c24d6 100644
> --- a/src/ipa/libipa/vector.cpp
> +++ b/src/ipa/libipa/vector.cpp
> @@ -312,6 +312,16 @@ namespace ipa {
>   * \return Product of matrix \a m and vector \a v
>   */
>
> +/**
> + * \fn Vector<T, Rows> operator/(T scalar, const Vector<T, Rows> &vector)
> + * \brief Divide a scalar by a vector element-wise
> + * \tparam T Numerical type of the contents of the vector
> + * \tparam Rows The number of rows in the vector

I'd rather see here "The number of elements ..." but not that important.

> + * \param scalar The scalar
> + * \param vector The vector
> + * \return The element-wise division of \a scaler by the \a vector
> + */
> +
>  /**
>   * \typedef RGB
>   * \brief A Vector of 3 elements representing an RGB pixel value
> diff --git a/src/ipa/libipa/vector.h b/src/ipa/libipa/vector.h
> index fe33c9d6fbd1..25882616ba8a 100644
> --- a/src/ipa/libipa/vector.h
> +++ b/src/ipa/libipa/vector.h
> @@ -308,6 +308,17 @@ Vector<T, Rows> operator*(const Matrix<T, Rows, Cols> &m, const Vector<T, Cols>
>  	return result;
>  }
>
> +template<typename T, unsigned int Rows>
> +Vector<T, Rows> operator/(T scalar, const Vector<T, Rows> &vector)
> +{
> +	Vector<T, Rows> result;
> +
> +	for (unsigned int i = 0; i < Rows; i++)
> +		result[i] = scalar / vector[i];
> +
> +	return result;
> +}
> +
>  template<typename T, unsigned int Rows>
>  bool operator==(const Vector<T, Rows> &lhs, const Vector<T, Rows> &rhs)
>  {
> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
> index cffaa06a22c1..319f7e0b5ef2 100644
> --- a/src/ipa/rkisp1/algorithms/awb.cpp
> +++ b/src/ipa/rkisp1/algorithms/awb.cpp
> @@ -316,11 +316,7 @@ void Awb::process(IPAContext &context,
>  	 * gain is hardcoded to 1.0. Avoid divisions by zero by clamping the
>  	 * divisor to a minimum value of 1.0.
>  	 */
> -	RGB<double> gains({
> -		rgbMeans.g() / std::max(rgbMeans.r(), 1.0),
> -		1.0,
> -		rgbMeans.g() / std::max(rgbMeans.b(), 1.0)
> -	});
> +	RGB<double> gains = rgbMeans.g() / rgbMeans.max(1.0);

How about the corner case when rgbMeans.g() < 1.0?  Then gains.g() won't
be 1.0 anymore.  Does it matter?

>  	/*
>  	 * Clamp the gain values to the hardware, which expresses gains as Q2.8
>
> base-commit: 9bc8b6a573a63b8c9f5588cdea6da5ae71abd138
> --
> Regards,
>
> Laurent Pinchart